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Научни трудове на Съюза на учените в България-Пловдив, серия Б. Естествени и хуманитарни науки, т. XVIII, ISSN 1311-9192 (Print), ISSN 2534-9376 (On-line), 2018. Scientific researches of the Union of Scientists in Bulgaria-Plovdiv, series B. Natural Sciences and the Humanities, Vol. XVIII, ISSN 1311-9192 (Print), ISSN 2534-9376 (On-line), 2018.
LITTER-FALL IN COMMON BEECH (FAGUS SYLVATICA L.) FOREST COMMUNITIE Si - A DEPOT OF IMPORTANT CHEMICAL ELEMENTS Violeta Dimitrova, Sonya Damyanova, University' of Forestry
Abstract
Litter-fall is the key parameter of bio-chemical circulation, connecting individual (components) of the forest ecosystem (trees, soil and water in the ecosystem). Litter-fall biomass and its chemical composition is necessary, to quantify the year cycling of individual elements and organic matter in the soil.
Dry weight and C, N, P, K, Ca, Mg, Mn, Fe, Cu and Zn content in the litter-fall were measured in four beech forest communities located in North-western part of Bulgaria.
Classic quantitative method was used for determination of the litter-fall stores. Organic carbon was determinate using oxidative decomposition, nitrogen by Keldal' method; phosphor and metals by emission optical spectroscopy.
Mean annual litter-fall was 263.39 g.m-2. Leaves represent the most significant fraction of the litter-fall, average 62%. The leaves' litter-fall returns in the soil on average С (35.04%), N (1.22%), P (0.078%), Ca (1.66%), K (0.23%), Mg (0.13%), Mn (591.7 mg.kg1), Fe (222.3 mg.kg" 1), Cu (8.6 mg.kg-1) and Zn (48.1 mg.kg-1).
Key words: litter-fall, nutrients, beech communities
Introduction.
Litter-fall is the key parameter of bio-chemical circulation, connecting individual parts of the forest ecosystem (trees, soil and water in the ecosystem). Litter-fall biomass and its chemical composition (including amount of heavy metals) is necessary, to quantify the annual cycling of individual elements and organic matter in the soil. Litter decomposition is the most important process when stating the flow of nutrients and organic matter in through the ecosystem and their input in the soil. This strongly affects the soil environment and production of the stands.
Many authors abroad (Kavvadias et al., 2001; Suslevska et al., 2001; Patricio et al., 2012) deal with the study of this component of the ecosystem. Positive correlations of litter-fall amount and sums of precipitation, circular area of stands, death of suppressed trees and the presence of epiphytic species, as well as negative correlation with the temperature during the summer season (Lebret et al., 2001; Novak et al. 2014) are established. The litter-fall quantities of deciduous forests are similar - 4.9 t.ha-1 for chestnut communities in Portugal (Patricio et al., 2012), 4. t.ha-1 for oak communities in Czechoslovakia (Novak et al. 2014).
Litter-fall is the first phase of the biogeochemical cycle and returns nutrients to the soil. Litter-fall is an important component of the nutrient cycle in forest ecosystems. Knowledge of these processes is essential for sustainable forest management.
Information on the dynamics of mineral nutrition elements is used both to explain the possible stress in forest ecosystems and to identify plant species requirements to environmental conditions. The content of macro- and microelements in different phytomass fractions is the subject of various researches in Bulgaria and abroad. Some authors study mostly the content of chemical elements in the litter-fall, as a more dynamic fraction (Lyubenova, Dimitrova, 2011). Subject of the discussion are tree species such as common beech (Fagus sylvatica L.) and common chestnut (Castanea sativa Mill.) (Lebret et al., 2001; Lyubenova et al., 2007; Damyanova et al.,
2014). Other studies focus not only on the chemical composition of wood, but also on other fractions, such as leaves, branches, flowers, fruits, and, in rare cases, roots [10]. In part of the publications, the content of the studied elements in the plant fractions and the content of the elements in the soil is correlated with the coefficient of biological uptake or bioaccumulation. The main elements considered are C, N, P, K, Ca, and from the micro elements - Pb, Zn, Mn, Fe, Cu. Inorganic elements are often studied as a component of the ash remaining after wood burning (Vassilev et al., 2010).
There are not enough researches in this area in our country. Information on the quantity of deciduous broadleaf species can be found in publications of Lyubenova et al., 2007 for chestnut communities, for beech trees (Dimitrova et al., 2009), and in other publications the chemical composition is mainly discussed (Кolarov et al., 2002; Malinova, 2009). This requires the carrying out of this type of study, which is part of the project: "Stocks and the role of dead biomass in forest ecosystems of common beech in Western Balkan Range".
This research aimed to estimate the inputs of litter-fall and quantities of main macro and micro elements - C, N, P, K, Ca, Mg, Mn, Fe, Cu, Zn.
Materials and methods. The litter-fall was gathered with two 1m2 litter-catchers from each sample plot. The fallen phytomas was collected and then fractionated on leaves, branches, fruits, seeds, cupolas and others, and dried for 48 hours at 85°C (leaves, annual branches) or 102°C (perennial branches, cupolas, seeds, wood, bark) to absolute dry weight (Rodin et al.,1968).
Determination of organic carbon: oxidative decomposition of the samples with a mixture of concentrated sulfuric acid and potassium dichromate and subsequent titration. Determination of nitrogen: method of Keldal - automatic distillation and subsequent titration using automatic Keltek-Tectator device. Determination of phosphor and metals: samples were wet digested with a mixer of concentrated nitric acid and hydrogen peroxide in microwave oven at different irradiation modes. The elements were measured using emission optical spectroscopy in inductively coupled plasma (ICP - OES).
Chemical analyzes were performed by the laboratory LETI Aquaterratest ICCE OOD, Sofia, Bulgaria.
Object. The studies were conducted in four sample plots located in beech communities on the territory of Forest Training and Education Enterprise "Petrohan" at Western Balkan Range. The region belongs to the temperate climatic zone. The soils are mainly (Cambisols, CM, WRB, 2006). The sample plots main characteristics are: SP 1 - 750 m a.s.l., 150 years, seed origin, canopy - 0.4, average height - 29 m, average diameter - 42 cm; SP 2 - 890 m a.s.l., 35 years, seed origin, canopy - 0.9, average height - 10 m, average diameter - 12 cm; SP 3 - 980 m a.s.l., 160 years, seed origin, canopy - 0.6, average height - 29 m, average diameter - 48 cm; SP 4 - 1440 m a.s.l., 130 years, seed origin, canopy - 0.8, average height - 27 m, average diameter - 32 cm.
Results and discussion. As result of the research carried out in the beech communities, we have obtained the results below.
Table 1. Litter-fall stores in investigated sample plots (abs.d.w*, g.m-2).
Litter-fall fractions SP 1 SP 2 SP 3 SP 4
Leaves 101.04 214.81 138.32 199.26
Bark 8.12
Branches 8.11 11.14 24.04 6.55
Seeds 22.55 15.85 43.43 13.09
Cupolas 93.07 23.03 87.2 43.98
Total 232.89 264.83 292.99 262.88
*abs. d. w. - absolute dry weight
The average total amount of the litter-fall was 263.39 g.m-2, ranging from 292.99 g.m-2 in SP 3 to 232.89 g.m-2 in SP 1 (Table 1). Leaves represent the most significant fraction of the litterfall, average 163.34 g.m-2 or 62%. The participation of the other fractions decreased in order of cupolas (24%) - seeds (9%) - branches (5%), as the ratio remains in all sample areas. The average amounts were respectively: 62 g.m-2, 24 g.m-2 and 12 g.m-2. The quantity of cupolas and seeds was highest in SP 3, which is normal because it is a seed base and the stands were of the highest age. The amount of bark in the litter-fall was negligible, on average less than 1%.
No correlations between the total amount of the litter-fall and factors such as altitude and stand age were established.
The data on litter-fall stores obtained in this study are similar to studies in other countries. For example, in France for beech forests results from 2.1 to 4.7 t.ha-1 (Lebret et al., 2001) are obtained, in Macedonia - 4.9 t.ha-1, of which the leaves are 3.4 or 70% (Suslevska et al., 2001), in Greece - 4 t.ha-1 (Kavvadias et al., 2001), in Spain - 2.8 t.ha-1 (Santa Regina et al., 2001). In our previous studies in other regions of the country, the amount of litter-fall in beech forests ranged from 3.2 to 4.2 t.ha-1 (Dimitrova et al., 2009).
The litter-fall of the studied communities was studied on the content of important macro-and micro- elements. The results obtained are presented in Table 2.
Table 2. Content of chemical elements in leaves' litter-fall at 4 sites
(C, N, P, Ca, K, Mg m %, Mn, Fe, Cu, Zn m mg.kg-1)
Elements Content
Site (SP) 1 Site (SP) 2 Site (SP) 3 Site (SP) 4 Average
Organic carbon (C) 37.10 33.05 34.10 35.89 35.04
Nitrogen (N) 1.46 1.32 1.04 1.06 1.22
Phosphorus (P) 0.074 0.082 0.080 0.074 0.078
Calcium (Ca) 1.87 1.67 2.12 0.99 1.66
Potassium (K) 0.19 0.14 0.20 0.37 0.23
Magnesium (Mg) 0.16 0.13 0.14 0.08 0.13
Copper (Cu) 11.8 6.9 7.4 8.1 8.6
Iron (Fe) 269.5 209.0 220.0 190.5 222.3
Manganese (Mn) 545.7 287.1 425.5 1108.6 591.7
Zink (Zn) 71.9 30.3 46.2 43.9 48.1
Leaf litter organic carbon concentrations did not differ significantly between four sites and had values from 34.10% to 37.10%. The N-content had the same characteristics: 1.04% to 1.46%. The higher amount of both nitrogen and organic carbon were measured for the litter-fall at the lowest situated beech stand were abiotic factors were favorable. Phosphorus content was relatively low, varying between 0.074% and 0.082% and the values were the same for the lower and higher situated stands. It was obtained the highest Ca amount among macrometals potassium, calcium and magnesium. The difference in values was doubled varying from 0.99% for site 4 to 2.12% for site 3. Amount of potassium varied moreover between 0.14% and 0.37%, where the highest concentration corresponded to the highest situated site. At the opposite, Mg concentration of litter-fall at 1440 m a.s.l. (site 4) was 0.08% comparing to the 0.16% at 750 m a.s.l. (site 3).
The data obtained were similar to the other country's data. For example: South Germany cited 46.7% carbon content for litter-fall (Berg, Gerstberger, 2004), Macedonia: 41.27% (Hristovski et al., 2014). Nitrogen amount we measured was about the same such as one for South Germany (1.33%) (Berg, Gerstberger, 2004), less than Central Italy (1.65%) (Berg et al., 1996) and higher than South Sweden (0.91%) (Staaf, 1982) and Macedonia (0.86%) (Hristovski et al., 2014). Variation between phosphorus' data cited by other countries were considerable: South Germany (0.09%) (Berg, Gerstberger, 2004), Central Italy (0.101%) (Berg et al., 1996), South Sweden (0.062%) (Staaf, 1982) and Macedonia (0.05%) (Hristovski et al., 2014). Calcium content in litter-fall at 1440 m a. s. l. (site 4) was the same to one measured at South Sweden (0.99%)
(Staaf, 1982), while at the lowest site was similar to that at Macedonia (1.84%) (Hristovski et al., 2014). Data for potassium cited for the other European countries differed as well as our investigation. Value for Central Italy (0.12%) (Berg et al., 1996) was closed to one obtained in that paper for the site 2, while that for site 1 were similar to one measured at Macedonia (0.18%) (Hristovski et al., 2014). The highest value obtained for K at site 4 located at 1440 m a. s. l. was higher than the most country except South Germany (0.5%) (Berg, Gerstberger, 2004). Mg content was a little bit less than the other countries: South Germany (0.09%) (Berg, Gerstberger, 2004) and Central Italy (0.18%) (Berg et al., 1996).
Data obtained for microelement Fe varied between 190.5 mg.kg-1 and 269.5 mg.kg-1. South Germany (Berg, Gerstberger, 2004) and South Sweden (Tyler, 2005) cited 110 mg.kg-1, while Macedonia (Hristovski et al., 2014) 1750 mg.kg-1. Mn content measured in that paper differ considerably from 287.1 mg.kg-1 to 1108.6 mg.kg-1. The lowest literature value was cited for Central Italy (50 mg.kg-1). The other countries published higher Mn content in beech litter-fall: 900 mg.kg-1 for Macedonia (Hristovski et al., 2014) and 1800 mg.kg-1 for South Sweden (Tyler, 2005) and 1850 mg.kg-1 for South Germany. Soil-formation is a specific process depends on a basic rock that's way it is a normal iron and manganese contents vary so much. Data obtained for zinc and copper were higher than those for Macedonia (4.08 mg.kg-1 for Cu and 69.63 mg.kg-1 for Zn) (Berg, Gerstberger, 2004) and South Sweden (6.3 mg.kg-1 for Cu and 36 mg.kg-1 for Zn) (Tyler, 2005). Conclusion
At the end of the vegetation season, the beech communities were returning on average 263.39 g.m-2 litter-fall. Leaves represented the most significant fraction of the litter-fall, average 62%. The leaves' litter-fall returns in the soil on average C (35.04%), N (1.22%), P (0.078%), Ca (1.66%), K (0.23%), Mg (0.13%), Mn (591.7 mg.kg-1), Fe (222.3 mg.kg-1), Cu (8.6 mg.kg-1) and Zn (48.1 mg.kg-1). The results obtained were similar mainly to those cited for South Sweden, for nitrogen was in the range for South Germany and for calcium was closed to values for Central Italy and Macedonia. Acknowledgements
The investigation was funded under the project № 19/19.01.2016: "Stocks and role of dead biomass in forest ecosystems of common beech in West Balkan Range", SIS-UF.
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